The present invention relates to insulation testing equipment is concerned, more particularly, with high potential dc insulation testers having remote controls and monitoring equipment for testing electrical cabling within a rotating mechanism.
Very often in the wire and cable industry, two insulated conductors will be twisted together to form what is called a twisted pair. The twisted pair is the basic component of many types of multi-conductor cables. The manufacture of a twisted pair is accomplished through the use of a machine called a "twinner" or pairing machine and while there are several ways in which two conductors may be twisted together, one method is enjoying increasing popularity. In this method, the individual conductors are fed from stationary spools or pay-offs through guides to a take-up reel which is mounted inside a gimbal-like assembly about which rotates a member called a bow. The bow is rotated about an axis along which the insulated conductors are fed from the spools to effect a twisting of the wires before they are wound on the take-up reel. One machine which operates in this manner is shown and described in U.S. Pat. No. 3,945,182 issued Mar. 23, 1976.
One test that the twisted pair must pass prior to shipment or use in other multi-conductor cables is an insulation test in which a high electrical potential is applied between the surface of the insulation and the conductor. If the insulation is defective, due to, for example, a pin hole, a spark will jump from the point of application through the defect to the conductor. Such testing is commonly called "spark testing" and defects in the insulation may be sensed, counted and measured through the pulse of current manifested by the spark.
It is most desirable to spark test the twisted pair as they are wound on the take-up reel to save time and keep production costs down. However, the only place that the wires exist as a twisted pair is inside the rotating bow, just before they are wound on the take-up reel. This presents certain problems in the spark testing of the wire.
One problem is that the high potential test electrode must be inside the bow, where space is limited, and there can be no directly wired connections to the electrode because of the bow rotation. This means that slip rings attached to the bow machinery must be used. Space limitations on existing machines dictate that only two low voltage slip rings are available for this purpose. Because of this, and because of the many functions a spark tester may be called upon to serve, existing designs for spark testers have controls and indicators inside the twinner bow. This makes adjustment of the controls inconvenient and time consuming because the high inertia machinery must be stopped each time an adjustment is made and then restarted.
The present invention overcomes these difficulties by locating all controls and indicators at a suitable remote location, so that adjustments may be made as the machinery is operated, and by locating the high potential components within the rotating mechanism. Other objects of the invention are to detect bare wire intervals of significant length, to determine whether the number of pin hole faults per unit length exceeds a given or preset value, and to provide signals or electrical contact closures for the control of the machinery whenever either of these fault conditions exist.